Since ancient times, it has been well established that the wind can be used to power a boat across the surface of water. Originally, sailboats were probably limited to sailing substantially downwind. The use of a rudder controlled boat direction, particularly when that was different from wind direction, and the development of a keel enabled sailboats to resist sideward movement, or leeway, when the wind varied significantly from being directly behind the boat's intended course. Eventually, it was learned that the use of fore and aft rigged sails that were cut to create a convex surface could be used to create a lift that would actually permit a sailboat to begin to sail to windward. The sail thus became a type of vertical wing. Modern sailboats can usually point to about forty-five degrees to the wind direction, with some boats being capable of doing even better than that. Of course, no conventional sailboat can sail directly toward the wind.
More recent hisory has seen the development of means other than wind to propel boats, such as steam and internal combustion engines. Far greater power could be developed, resulting in much greater speed. Similarly, the science of hydrodynamics was refined to the point that boat hull design became mathematically analytical rather than exclusively empirical, and this in turn resulted in advanced hull designs that reduced both frictional and appendage drag. The efforts to reduce both types of drag, and therefore increase boat hull speed, have been applied to sailboats as well as power boats.
One obvious way to reduce both appendage drag (representing the amount of water that the hull pushes out of the way as it moves through the water) and friction drag (which is a function of wetted surface area of the hull) is to raise the boat out of the water. A so-called displacement type hull has its weight supported by a force equal to the weight of the water displaced by the hull. However, if some of the weight of the hull can be borne by other means, the hull will rise out of the water somewhat, reducing both the amount of water displaced (which must be moved out of the way) and also the wetted surface area. Some prior art in regard to sailboats is directed to this objective.
For example, U.S. Pat. No. 4,610,212 issued to Petrovich teaches the use of a rather sophisticated mechanism that includes a hang glider type sail on a catamaran style hull. The same principle underlies the Physail by Eric Olsen, as described in the January, 1985 issue of "Sail" magazine at page 91. Both utilize lift from the sail to help support boat weight and thus reduce drag To a degree, the same principle is recognized as applying to sailboards, as described in on article on an experimental boat termed a flying proa by Chris White on page 88 of the same issue of "Sail" magazine.
A hypothetical idealized version of this concept is also shown in Aero-Hydrodynamics of Sailing by C. A. Marchaj, Copyright 1979 and published by Dodd, Mead & Co. On pp. 125-27, a sailing skimmer is described in which an aerofoil is supposed to lift the hull completely out of the water except for a dagger board keel and rudder.
The concept of reducing drag in a sailboat by using vertical lift is one of several important objectives of the present invention, but the structure used to accomplish same is vastly different than these prior art references. In reality, these references only emphasize the importance of the accomplishment. The means employed by the present invention, an autogyro rotor, has never been employed in the manner here taught, so far as is known.
Actually, there is one known instance wherein an autogyro rotor has been employed in conjunction with a boat hull but with a different structure and for a different purpose. This is described in the August, 1984 issue of "Popular Rotorcraft Flying" magazine at pp. 9-13. However, the boat hull is really nothing more than a pontoon for a gyrocopter whose propulsion is by a towline from a power boat. The autogyro rotor is used for lift, but the structure described is an airborne vehicle, not capable of being propelled while waterborne by the wind for reasons which will become apparent as the present invention's features and essential structure are described. These features include the ability to activate and neutralize the autogyro rotor with respect to the wind, the ability to control rotor orientation to hull centerline responsive to differing wind direction and hull course, and the simultaneous retention of rotor resultant force from the wind through the center of lateral resistance of the hull and rudder combination for all rotor support orientations. The benefit of the latter is to eliminate conventional sailboat heel and yawing due to either a weather or a lee helm. Also eliminated and, in fact, reversed, is the downward force of a conventional sail when the sailboat is heeling.